With just weeks left before the Iowa caucuses, candidates were anxious to sway borderline voters and jumped at the chance for screen time – even if that meant drawing blood.

Trump rules out independent run

Trump committed – again – to backing the eventual Republican 2016 presidential nominee, even if it’s not him.

Hugh Hewitt, co-moderator of the debate, asked front-runner Trump if he’s ready to put to rest speculation that he would run as a third-party candidate, which would likely hand the election to Democrat Hillary Clinton. Trump replied simply, “I really am.”

The tycoon previously signed a pledge stating as much, but recently dangled the possibility of an outside run after rumors surfaced that party leaders were plotting to keep him off the ticket.

The crowd immediately erupted into applause following Trump’s pronouncement.

The real estate mogul put a cherry on top by adding, “I am totally committed to the Republican Party,” but still predicted it will be a non-issue, saying he’ll finish on top and then rout Clinton in the general election.

Split-screen sparring

Combativeness was not in short supply – and CNN made sure of it.

Throughout the Republican debate, moderators asked a question, solicited opposing comments, then cut to side-by-side boxes showing the two candidates involved.

After a month of ads hyping the debate, the network appeared intent on creating friction. In the end, CNN delivered and viewers got what was promised.

Opponents pile on Rubio

Texas Senator Ted Cruz had poll-driven momentum and talk radio chatter on his side going into Tuesday evening. But in the debate hall, it was Sen. Marco Rubio, of Florida, who drew the audience’s biggest cheers from the beginning.

That enthusiasm wasn’t lost on Rubio’s opponents, drawing take-downs from Cruz and Sen. Rand Paul.

Just minutes into the action, Cruz and Rubio had it out over the true meaning of national security and surveillance programs allowed by federal law. Each senator insisted that the other’s vote curtailed NSA activity and thereby endangered national security.

Paul was quick to bring up Rubio’s now-abandoned gang of eight Senate plan that would have eventually led to undocumented immigrants gaining legal status, saying, “Marco has more of an allegiance to Chuck Schumer and to the liberals than he does to conservative policy.”

Co-moderator Dana Bash pinned down Rubio on his position regarding citizenship for illegal immigrants, extracting the answer, “I, personally, am open to allowing people to apply for a green card.” However, the freshman senator clarified that green cards would be a long way off.

Cruz said he does not support legal recognition of anyone who enters the U.S. illegally.

As in previous skirmishes, Rubio artfully dodged most jabs, but immigration remains an issue competitors perceive as his big weakness among the base.

Bush and Trump rumble

For the first hour of the debate, Trump was rarely seen or heard. But that silence came to a halt with a fiery personal clash involving Trump and Jeb Bush.

Bush and Trump tangled over national security, immigration, allotted time and presidential temperament.

The split-screen showed Trump’s face contort into visible objections, which quickly went viral online, as Bush launched a barrage of critiques, calling him “a chaos candidate” who can’t insult his way into the presidency.

While Christie appeared pleased with his answer, Rand Paul snapped, “If you’re in favor of WWIII, you have your candidate.” Unfazed, Christie replied that the White House’s current strategy is irresponsible, calling for an immediate about-face.

As Christie climbs the polls in New Hampshire, he’s looking to build his standing by appealing to voters seeking a resolute, non-Trump, leader.

Lindsey Graham goes off

In the undercard debate held earlier Tuesday night, Sen. Lindsey Graham went on several highly quotable tears about his longtime support for American boots on the ground in the Middle East.

No one was spared, except former President George W. Bush, who Graham says he misses.

Graham instructed CNN’s moderators to ask Cruz why he would he would leave Syrian ruler Bashar al-Assad in power, since it would mean acquiescing to his backers, Iran and Russia. Graham quoted Cruz’s favorite movie “The Princess Bride,” admonishing his colleague, “Princess Buttercup would not like this.”

Russian President Vladimir Putin also incurred Graham’s wrath, with the South Carolina senator cutting the macho world leader where it hurts. Graham cracked, “I’m not afraid of a guy riding around on a horse without a shirt.”

Phantom cougher

Someone had a tickle in their throat and coughed intermittently for 2.5 hours. Of course, Twitter went wild with speculation about the perpetrator’s identity.

ESPN’s Robert Flores named the culprit: Dr. Ben Carson, who rarely spoke during the debate.

During the break can we get Dr Carson medicine for his whooping cough? #GOPDebate